The particularity of the window’s NLB protocol leas to the cluster host business connected S93 switch abnormal

Publication Date:  2012-12-13 Views:  325 Downloads:  0
Issue Description
+ internal network+
    +            +
  +                + 
S93-1++++++S93-2
  +                +
  +                +
  +                +
cluster host-1+++cluster host-2
  +                +
    +            +
       + public network+
The cluster hosts provide the function of proxy server. Two S93 play as VRRP.
Alarm Information
The cluster hosts work not in normal.
Handling Process
1 Checking the ARP entry and we will find that the S93 haven’t learnt the cluster host’s ARP normally. After updating the patch, S93 can deal with these packets and then the ARP learning is normal.
The relevant information of ARP and MAC:
Cluster host 1 IP 1.1.1.2 MAC:02bf-0a46-ed3a
Cluster host 2 IP 1.1.1.3 MAC:02bf-0b46-ed3a
Cluster IP address: IP 1.1.1.1 MAC:02bf-0146-ed3a
The ARP that S93 have learnt: 02bf-0146-ed3a ---1.1.1.1
2 But this time the business is still intermittent. After understanding the NLB protocol, we find that the host run NLB protocol is under L2 switch.
We can solve this problem by adding two L2 switch and networking as follows:
S93-1++link 4 ++S93-2
  +                +
  +                +
link 1         link 3
  +                +
  +                +
S33-1++link 2++S33-2
  +                +
  +                +
  +                +
  +                +
  +                +
cluster host-1+++cluster host-2
In the network show above, S93 can learn ARP normally, 02bf-0146-ed3a ---1.1.1.1---terminal of link 1
S93 forwarding downstream packets to S33-1 by link 1. S33-1 can’t check the MAC: 02bf-0146-ed3a.

Root Cause
1 The hosts cluster abnormal
2 S93 forwards information abnormal
Suggestions
Key point 1: In the packets forwarding by the host which is used as NLB load balance protocol, the source MAC of L2 header is not the same as the MAC in the protocol. This situation need the switch deal with the ARP.
Key point 2: Windows recommend the hosts run NLB protocol work under L2 switch.

END